Process of producing homogeneous products, including films



ucts of various kinds, but particularly films UNITED STATES PATENT OFFICE.

HERMAN 'WILLKIE', 0F BALTIMORE, MARYLAND, ASSIGNOR TO S. INDUSTRIAL ALCOHOL (10., A CORPORATION OF WEST VIRGINIA.

PROCESS OF PRODUCING HOMOGENEOUS ?RODUGTS, INGLUDING FILMS.

No Drawing.

To all whom it may concern:

Be it known that I, HERMAN F. VILLKIE, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented a certain new and useful Improvement in Processes of Producing Homogeneous Products, Including Films, of which the following is a specification.

My invention relates particularly to a process of producing homogeneous prodor coatings from coating compositions containing cellulose esters.

The object of my invention is to provide a process by means of which homogeneous products of various kinds, and particularly films or coatings may be obtained. The object is especially to produce such films or coatings from compositions containing cellulose esters, and especially nitrocellulose, which roducts will be free from cloudiness. nother object is to produce prodnets, and particularly films or coatings in this way from compositions, using as a solvent one or more esters, alcohols, ethers and ketones alone, or mixed together, which are of such a. character that the solvent in evaporating will carry off the water contained in the coating composition to such an extent as to obviate leaving behind a product having a cloudy appearance owing to the presence of water. A further object is to use a solvent that will form with water a constant boiling mixture so that the water will most effectively evaporate with the solvent in order to avoid leaving behind a cloudy product of the character above referred to. Still another object is to remove substantially all the water present in the solvent itself in the product dissolved therein, as for example, the cellulose ester, and taken up from the atmosphere owing to the hygroscopic character of the solvent used. Again a further object is to use ethyl acetate as one of the solvent constituents, notwithstanding its great avidity for moisture.

Hitherto, it has not been found possible to produce without the aid of a vacuum films free from cloudiness by the use of merely a low boiling solvent, inasmuch as when the low boiling solvents were previously used, they would evaporate quickly, leaving behind particles of water which would impart to the film a cloudiness. As

Specification of Letters Patent.

Patented Dec. 13, 1921.

Application filed April 12, 1920. Serial No. 373,084.

a consequence such films were not dense and homogeneous. Furthermore, such films would not take as even color when pigments were present in the coating composition, as the cloudiness which would vary in different portions of the film would produce a variation in the shade of the color used. In order to obviate this effect, it has been customary in the past to include with the low boiling solvent a high boiling solvent, so as to allow the water and low boiling solvent to entirely evaporate before the film became hard. It is one of the objects of my inventlon to avoid the necessity of using such additional high boiling solvent or solvents.

Further objects of my invention will appear from the detailed description thereof contained hereinafter.

lVhile my invention is capable of embodiment in many difi'erent forms, for the purpose of illustration I shall describe only certain forms of the same hereinafter.

For example, in carrying out my invention I may make a coating composition by providing a solvent mixture containing- 98% by weight of ethyl acetate, 2% by weight of alcohol, having a strength of 95%, in 100 parts by weight of which solvent mixture I may dissolve-8 parts by Weight of pyroxylin. In the above composition, the proportions of the ethyl acetate in the solvent mixture may vary considerably, and may be higher or lower, or even as low at 40%, the proportion of the alcohol being increased in that event to The alcohol ma be entirely absent or may be substituted by any other liquid which would not be detrimental to the solvent action of the ethyl acetate, as for example, benzol. It will also be understood that the proportion of the pyrox lin present may be varied to a considera le degree. Instead of the ethyl acetate, I may substitute in part, or as a whole, one or more other substances that may have .a dehydrating action, as for example, one

or more esters other than ethyl acetate one The coating composition made in this manner when spread upon a surface to prowhen there is sufficient alcohol and water present, or

v92% by weight of ethyl acetate,

. 8% by weight of water, when there is no alcohol present, and the mixture will evaporate, thus removing from the film or coating not only the water present in the solvent mixture, but the water present in the pyroxlin, as well as any water which is taken up by the ethyl acetate during the formation of the film or coating. The film formed in this manner is found to be entirely clear and free from cloudiness. Therefore, films made in this way, and which may have any other desired constituents added thereto, such' as pigments, softening materials, body-giving materials, etc., in accordance with the usual practice in the production of films and coatings, will have auriiform color, andwill not be lackin in homogeneity due to the presence of bub les or droplets of water. The solvent which evaporates from the film while the latter is drying or hardening may be recovered in any suitable manner by collecting and condensing the same, and the condensate may be used over again several times for the production of films. When the -solvent mixture has accumulated a considerable percentage of water, however, it may be treated in any suitable manner for the removal of some of the water, so as to permit the solvent mixture to be used over again in the production of films, or the solvent mixture containing water may be used in some other industry without the removal of water therefrom, as for example, extracting oils, fats, and waxes.

Furthermore, it will be understood that my invention is broadly applicable to the production of varnishes, paints or cements as set forth in my application .Ser. No.

373,083, filed April 12, 1920,

While I have described my invention above in detail, I wish it to be understood that many changes may be made therein without departing from the spirit thereof. I claim: 1. The process which comprises forming film by evaporating a solution of a cellulose ester in a solvent consisting of an ester having a dehydrating action and an alcohol adapted to form a constant boiling mixture with and carry off water during the evapora tion of the solvent.

2. The process which comprises forming a film by evaporating a solution of a cellulose ester in a solvent consisting of ethyl acetate and ethyl alcohol proportioned to form a constant boiling mixture with and carry off water during-evaporation of the solvent.

In testimony that I- claim the foregoing, I have hereunto set myhand this 11th day of March, 1920.

HERMAN F. WILLKIE. 

